1. Field of the Invention
The present invention relates to an abnormality treatment device for a control device for an automatic transmission, and more particularly to an abnormality treatment device capable of preventing a danger to enable a vehicle to travel continuously when there is any abnormality in an electronic control device for electrically treating a hydraulic pressure control for an automatic transmission whose power transmission passage of a speed change gear mechanism is changed to change speeds by means of hydraulically operated friction elements and a speed change judgement for exchanging hydraulic pressure supply to the friction elements. This invention relates also to an abnormal value detection device for detecting an abnormality of signals corresponding to engine loads and vehicle speeds for an electronic control device which electrically detects the engine loads and vehicle speeds to carry out a speed change judgement in a speed range selection judgement circuit with the aid of the detected values, and more particularly to an abnormality judgement device for detecting abnormality of signals for a line pressure control device which detects hydraulic pressure (line pressure) which actuates friction means for changing power transmission passage of a speed change gear mechanism to control the detected hydraulic pressure so as to be a hydraulic pressure value corresponding to an engine load.
2. Description of the Prior Art
A hitherto used automatic transmission and an electronic control device therefor will be summarily explained hereinafter.
FIG. 1a illustrates a power transmission system for an automatic transmission of three forward and one reverse speeds hitherto used. A torque converter comprises a pump impeller 104 connected to an engine crankshaft 101, a turbine runner 103 connected to an input shaft 107 and a stator 102 secured to a stationary portion through a one-way clutch 105 for transmitting a rotating torque to a planetary gear mechanism 120. The planetary gear mechanism 120 consists of two planetary gear sets and five friction elements. The two planetary gear sets have been known and consist of the following rotating members, i.e. a front carrier 112, a rear carrier 112', a front internal gear 111, a rear internal gear 111', a front pinion 114, a rear pinion 114', and a sun gear 113 as shown in FIG. 1a. The friction elements consist of a band brake 108 for fixing the sun gear 113 when the band brake 108 is actuated, a front clutch 109 for connecting and disconnecting an intermediate shaft 107 driven by a torque converter 100 with the sun gear 113 for transmitting power therebetween, a rear clutch 110 for transmitting and interrupting power from the intermediate shaft 107 to the front internal gear 111, a low and reverse brake 115 for fixing the rear carrier 112' when the brake 115 is actuated, and a one-way clutch 105 for permitting the rear carrier 112' to rotate in the same direction as the rotating direction of the engine crankshaft 101. The rotating torque is transmitted from the planetary gear mechanism 120 to an output shaft 118. An oil pump 106 supplies operating oil to the torque converter 100, the respective bearings and gears, the friction elements 108, 109, 110 and 115 and a hydraulic circuit later described. A parking pole 116 is in mesh with a tooth 117 of a parking gear to fix the output shaft 118 when a shaft lever later described is in a P (parking) range.
FIG. 1b illustrates a hydraulic control circuit for supplying a hydraulic pressure to the friction elements of the automatic transmission of FIG. 1a.
In the drawing of FIG. 1b, parts of lines which are at the same pressures have been designated by the same reference numerals for the sake of clarity. As the operating principles of the respective valves of this circuit have been known, they will be not described in more detail.
A constant pressure valve (pressure regulator valve) 131 maintains the operating hydraulic pressure delivered from the oil pump 106 at a desired pressure (line pressure 6). The hydraulic oil delivered from the oil pump 106 passes through a passage 18 and acts on a land 131a of a valve spool to push it downwardly against a force of a valve spring 131b and thereafter is drained through a drain port designated by x. This action is repeated until the line pressure is balanced by the force of the spring 131b and maintained. A line 20 is in communication with the torque converter 100 to keep the inside of the converter 100 at a desired pressure while part of the operating oil is supplied through a ball valve to the front clutch 109 and rear clutch 110 for their lubrication.
When an acceleration pedal (not shown) is pressed down, a throttle pressure 15 rises and acts on an underside of one land of a plug 131c to assist the force of the spring 131b in raising the valve spool, thereby reducing a clearance for the drain port x to cause the line pressure 6 to rise.
When a manually operated valve 132 later described is operated into an R (reverse) range, the line pressure 6 from a line 5 acts on the lower surface of the other land of the plug 131c so as to assist the force of the spring 131b to further increase the line pressure 6 in the same manner as above described.
The manually operated valve 132 has a valve spool 132a mechanically connected to a manual lever (not shown) so as to be reciprocatively moved to distribute the line pressure 6 through lines 1, 2, 3, 4 and 5 as follows.
line 1.fwdarw.1-2 shift valve 133, 2-3 shift valve 134 and rear clutch 110 PA1 line 2.fwdarw.2-3 shift valve 134 PA1 line 3.fwdarw.throttle back up valve 136 PA1 line 4.fwdarw.emergency valve 137 PA1 line 5.fwdarw.pressure regulator valve 131 and 1-2 shift valve 133
These lines receive the line pressure 6 in response to respective operating positions (ranges) of the manual lever as shown in Table 1.
TABLE 1 ______________________________________ Position of shift lever Line P R N D II I ______________________________________ 1 o o o 2 o o 3 o o o o 4 o o o 5 o ______________________________________
As can be seen from the Table 1, moreover, when the shift lever is in an N (neutral) position, all the line pressure 6 is drained through drain ports x.
A line pressure regulator valve (vacuum throttle valve) 135 forms the line pressure 6 into a throttle pressure 15 in proportion to an engine load, which acts on a land 131d of the valve spool of the constant pressure valve 131 to regulate the line pressure 6 in proportion to the engine load. The line pressure regulator valve 135 has a valve spool 135a connected to and operated by a diaphragm type actuator 140 which is actuated by negative pressure. When the negative pressure acting upon a diaphragm 140a of the actuator 140 is at a small value (the engine load is large), the valve spool 135a is in its lowered position (as shown in the right half of the spool in the drawing) as the result of a lowering action of a spring 140b of the actuator 140, so that the line pressure 6 is fed as the throttle pressure 15 into the constant pressure valve 131 to obtain a high line pressure 6. When the negative pressure acting upon the diaphragm 140a of the actuator 140 is at a large value (the engine load is small), the valve spool 135a is raised by the diaphragm 140a into its raised position (as shown in the left half of the spool in the drawing), so that the line pressure 6 becomes lower by a value corresponding to the pressure flowing into the line 16 and is fed as the throttle pressure 15 into the constant pressure valve 131 to obtain a low line pressure 6.
An intake manifold negative pressure of an engine is introduced through a check valve into a negative pressure tank 138 and retained therein, from which the negative pressure is further introduced to the diaphragm 140a of the actuator 140 through a solenoid valve 144 adapted to open when a current is supplied. To the diaphragm 140a furthermore the atmosphere is introduced through a solenoid valve 143 which introduces the atmosphere when a current is supplied. Both solenoid valves 143 and 144 are so controlled that the negative pressure acting upon the diaphragm 140a corresponds to the engine load in a manner that the larger the engine load, the smaller is the negative pressure acting upon the diaphragm 140a, thereby enabling the throttle pressure 15 to correspond to the engine load.
At a moment when the manually operated valve 132 is shifted from the D range to II or I range, the line pressure 6 is fed through a line 3 into the throttle back up valve 136 to raise a valve spool 136a against a force of a spring 136b to a level shown in the left half of the spool in the drawing, thereby producing a back up pressure 16 lower than the line pressure 6 while part of the line pressure 6 is being drained through a drain port shown at x. When the valve spool 135a of the pressure regulator valve (vacuum throttle valve) 135 is at its raised position, this back up pressure 16 acts as a throttle pressure 15 upon the constant pressure valve (pressure regulator valve) 131 to obtain a high line pressure 6, thereby preventing any delay in operation of the brake band 108 or low and reverse brake 115.
In addition, with the spool 132a of the manually operated valve 132 in I range, when the later described 1-2 shift valve 133 has shifted toward a first speed side, the line pressure 6 is fed from the manually operated valve 132 through a line 1 to a line 8. With the spool 132a in I range, moreover, the line pressure 6 from the manually operated valve 132 through a line 4 acts on a valve spool 137a of the later described emergency valve 137 to lower it as shown in the left half of the valve spool in the drawing. The line pressure 6 fed into the line 8 as above described is therefore introduced into a line 9. In this manner, the line pressure 6 through the line 9 raises the valve spool 136a of the throttle back up valve 136 to the uppermost position to communicate the line 16 with the drain port at x, thereby preventing an occurrence of a back up pressure 16 so as not to produce an excess line pressure.
In addition to the above case of I (first speed) range of the manually operated valve, with R (reverse) range the valve spool 137a of the emergency valve 137 is also at the depressed position. With the R range of the spool of the valve 132, therefore, the line pressure from the manually operated valve 132 is fed through a line 5 into a line 19, thereby actuating the front clutch 109 to release the brake band 108.
With ranges of the manually operated valve 132 other than N (neutral), P (parking) and R (reverse) ranges, the line pressure 6 always supplied through the line 1 is drained through an orifice 133a or 134a when a current is supplied to a 1-2 shift solenoid 141 or 2-3 shift solenoid 142 to maintain a spool 133c of the 1-2 shift valve 133 or a spool 134c of the 2-3 shift valve 134 at a location shown in the right half of the spool in the drawing. When a current is supplied to the shift solenoid 141 or 142, however, the orifice 133a or 134a is closed to cause the line pressure to act on an upper end of the valve spool 133c or 134c, thereby lowering the valve spool to the position shown in the left half of the valve spool in the drawing to supply the pressure to the respective friction elements (rear clutch 110, brake bank 108 and low and reverse brake 115).
Combinations of operations of the shift solenoids and friction elements with the manually operated valve 132 in the respective operating positions are shown in Table 2.
TABLE 2 __________________________________________________________________________ Shift Low and Band servo Operated solenoid Clutch reverse 108 position 1-2 2-3 Front Rear brake Actua- One way (Range) 141 142 109 110 115 tion Release clutch __________________________________________________________________________ P OFF OFF o R OFF OFF o o o N OFF OFF D 1st ON ON o o speed 2nd OFF ON o o speed 3rd OFF OFF o o o o speed 2 2nd OFF ON o o speed 3rd OFF OFF o o o o speed 1 1st ON OFF o o speed 2nd OFF OFF o o speed __________________________________________________________________________
In Table 2, ON and OFF mean the supply of current and not supply of current, respectively, and circles indicate the operations of the relevant elements. The band servo or brake band 108 is released in view of pressure receiving areas when a hydraulic pressure acts regardless of the actuation and release.
An electronic control device for controlling the above automatic transmission will be explained hereinafter wherein after determining a gear changing position depending upon an engine load and a vehicle speed, the shift solenoids 141 and 142 are energized or deenergized, while the negative pressure acting upon the actuator 140 is controlled by energizing or deenergizing the atmosphere solenoid 143 and negative pressure solenoid 144 to maintain the required line pressure.
As an embodied circuit arrangement of the electronic control device is not essential for an understanding of the invention, it will not be described in further detail, but only its control system will be explained. Circuit arrangements may be used for this purpose, which have been proposed by Nissan Motor in Japanese Patent Applications Nos. 41,345/79 and 39,351/79, corresponding, respectively, to U.S. patent application Ser. Nos. 136,337 filed Apr. 1, 1980, and 134,986 filed Mar. 28, 1980.
FIG. 2 illustrates an outline of the electronic control device 208 consisting of a speed range selection judgement circuit 209 for determining speed ranges by energizing and deenergizing the shift solenoids 141 and 142 and a hydraulic control judgement circuit 210 for controlling the line pressure by energizing and deenergizing the atmosphere solenoid 143 and the negative pressure solenoid 144.
The speed range selection judgement circuit 209 receives a manual lever position signal (D range signal 202, II range signal 203 or I range signal 204) to select a speed change line representative of a relation between the engine load and vehicle speed as shown in FIGS. 3a and 3b and compares the speed change line with a vehicle speed signal 205 and an engine load signal 206 to determine a speed change range and thereafter produces an output signal 141' or 142' to energize or deenergize the shift solenoid 141 or 142.
The speed change lines in FIG. 3a are for the D range and the speed change lines in FIG. 3b are for the II and I ranges. For example, with the D range in FIG. 3a, if a vehicle speed increases from x.sub.1 to x.sub.2 with a constant engine load, at a moment when the vehicle speed crosses a speed change line a, the speed range is changed from the first range to second range. A speed change line b determines the speed change from the second range to third range in the same manner. Speed changes from the second to the first and from the third to second are determined by the speed change lines a' and b' which are positioned on lower vehicle speed sides as can be seen from FIG. 3a which result from a hysteresis in a down-shift. With the II and I ranges, speed changes are also effected by the use of speed change lines d, d' and c, c' in FIG. 3b in the same manner.
The hydraulic control judgement circuit 210 receives the engine load signal 206 and a line pressure signal 207 corresponding to a line pressure to compare the line pressure value of the line pressure signal 207 with a line pressure value corresponding to an engine load obtained from a required line pressure characteristic with the engine load as shown in FIG. 4 to produce an output signal 143' or 144' for energizing or deenergizing the negative pressure solenoid 143 or atmosphere solenoid 144 to operate the hydraulic pressure regulator valve 135 so as to obtain a line pressure corresponding to the engine load. A shaded zone in FIG. 4 is an insensible zone wherein both the solenoids 143 and 144 are not simultaneously energized for preventing a superfluous power consumption.
The above manual lever position signals 202-204 are obtained from sensors such as switches which are adapted to be turned on when the manually operated lever assumes respective positions. The vehicle speed signal 205 is obtained from a sensor such as a reed switch adapted to be repeatedly turned on and off by means of a magnet rotated together with an output shaft of the transmission. The engine load signal 206 is obtained by detecting an open degree of a throttle of the engine by means of a potentiometer type sensor or by detecting a displacement of a diaphragm subjected to an intake manifold negative pressure by means of a potentiometer type sensor. The line pressure signal 207 is obtained by detecting a displacement of a diaphragm directly subjected to the hydraulic pressure by means of a potentiometer or detecting a displacement of a diaphragm subjected to a negative pressure acting upon the actuator 140 of the line pressure regulator valve 135 by means of a potentiometer type sensor.
The hitherto used automatic transmission and electronically controlled circuit therefor are constructed as above described and have encountered the following problems.
When the electronic control circuit 208 is inoperative owing to its failure or a failure of its power source, the shift solenoids 133 and 134 are deenergized so as to be inoperative. In this case, however, the vehicle can be driven by an operation of the manually operated valve 132 at the third speed in D range, second speed in II range or first speed in I range. At this time, the solenoids 143 and 144 of the line pressure regulator valve 135 are deenergized to maintain the line pressure enabling the vehicle to normally travel. However, if the input signals 202-207 to be fed to the electronic control circuit 208 are extraordinary, the following great problems arise with the travelling of the vehicle. Namely, when the lines of the input signals are broken down or short-circuited or the respective sensors have failed, corresponding input signals having extraordinary values are obtained, based upon which an incorrect judgement in speed change or a wrong line pressure control will be effected. In case, for example, that the engine load signal 206 is inputted as a voltage proportional to an engine load, if the signal line is broken down, the engine load is deemed as if it were a light load, so that a shift up to a higher speed range (second or third range) is effected at a low speed even if other input signals are correct. On the other hand, as the line pressure is controlled to a low pressure, so that in an extreme case the friction elements of the transmission are likely to slide, it is often impossible to climb an ascent or to start requiring a great driving torque. If this condition occurs in driving downhill, the friction elements tend to slide due to the low line pressure although the spool of the manually operated valve 132 is shifted to the II range, so that an engine braking cannot be obtained thereby urging a driver to drive dangerously. Moreover, when the vehicle is driven at a constant speed before such a condition occurs, the required torque for such a driving is so small that the driver cannot previously notice the falling of the line pressure. This is dangerous. Furthermore, if the control is effected as if the manually operated lever were in a position different from an actual one owing to a short-circuit of the manual lever position signals 202-204, correct speed changes cannot be obtained. Moreover, if the input signal lines of the vehicle speed signal 205 and line pressure signal 207 are extraordinary, the proper speed change and line pressure control cannot be effected, respectively.